艦娘は本質的に深海棲艦と同種であるため、敵海域での長時間戦闘は艦娘の深海棲艦化に繋がる。この汚染度を棲性深度といい、臨界点に達すると鎮守府への帰還能力が自動的に剥奪される。

Since Kan-Musu and abyssal ships are essentially the same beings, prolonged combat in enemy territory induces abyssalization of fleet girls. The severity level of this kind of pollution is called the abyssosis depth. When it reaches a critical point, the sufferer is automatically deprived of her ability to return to the naval base.